1. Field of the Invention
The present invention relates, in general, to the field of recovery boiler auxiliary systems, the use of black liquor as a fuel, and in particular to a new and useful nozzle for directional flow of black liquor into a recovery furnace.
2. Description of the Related Art
The basic splash plate spray nozzle has been used in recovery boilers since 1929 and a patent granted thereon to G. H. Tomlinson and L. S. Wilcoxsin. A splash plate spray nozzle is used to deliver black liquor fuel to the furnace, where it is dried to particles called char (devolatized liquor consisting of carbon bound to inorganic chemicals) by the heat emitted from existing char burning below it. A typical delivery system, including a splash plate spray nozzle, is shown in Steam, 40th Ed. in FIG. 17 at page 26-15, shown as FIG. 4 herein. Air ports on the side walls of the furnace facilitate char combustion on the floor of the furnace.
Problems arise when the char bed piles in the center of the furnace, away from the air flow at the side wall ports, requiring an excessive secondary air source to control the size of the char bed by burning the material and this in turn causes excessive sodium fuming of liquor carryover to the convection passes, which leads to fouling of heat transfer surfaces.
The standard splash plate spray nozzle has no directional control of the flow of black liquor, and often large char beds are created on the furnace floor away from the side walls and the primary air ports, requiring additional secondary air to burn the material and control the char bed height. Also, within a standard splash plate spray nozzle in a large furnace, black liquor droplets must traverse greater distances to reach the far side walls than the adjacent side walls of the furnace; this results in excessive droplet combustion in flight, rather than the droplets reaching the furnace walls, where they then drop to the furnace floor near the air ports to be burned properly.
Another type of nozzle is disclosed in an application by Babcock & Wilcox, Ser. No. 08/347,761 filed Nov. 30, 1994, for a wedge splash nozzle.